Radial face rotary buffing element



Oct. 6, 1959 Filed Dec. 23, 1957 E. W. HALL ET AL RADIAL FACE ROTARY BUFFING ELEMENT 2 Sheets-Sheet 1 Inventor.- 3mm WHaZZ DomzuwR.Pwone,

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RADIAL FACE ROTARY BUFFING ELEMENT Filed Dec. 23, 1957 2 Sheets-Sheet 2 l'zwemofls: E'Zdlsfia WHQZZ, 120mm! R. Paone,

United States Patent RADIAL FACE ROTARY BUFFING ELEMENT Elisha W. Hall, Scituate, and Dominick R. Paone, East Weymouth, Mass., assignors to F. L. & J. C. Codman Company, Rockland, Mass, a corporation of Massachusetts Application December 23, 1957, Serial No. 704,522

3 Claims. (Cl. 51-195) This invention relates to a rotary buffing element for operating on work presented to its radial face, which work-engaging face is formed of grit-coated fabric such for example as emery cloth or sandpaper. The word bufiing is used above in a generic sense to include various abrasive operations. By grit-coated fabric reference is made to flexible sheet material, either woven fabric as in emery cloth or strong paper as in sandpaper having adhesively secured thereto hard particles of abrasive material such as emery, silicon carbide, aluminum oxide, garnet, flint, rouge and tripoli. The particle size and the hardness of the particles may vary to suit the particular work in hand.

The object of the invention is to provide an efficient and long lasting element which will economically utilize such grit-coated fabric.

The invention will be well understood by reference to the following description taken in connection with the accompanying drawings wherein:

Fig. 1 is a schematic view showing an embodiment of the invention as being driven by means of a flexible shaft for operating on a piece of work;

Fig. 2 is a front elevation of the rotary element, only half being shown;

Fig. 2a is an elevation of one of the slips used in the manufacture of the element shown in Fig. 2;

Fig. 3 is a view similar to Fig. 2 with parts successively omitted or broken away to disclose the structure;

Fig. 4 is an exploded view taken along the line 4-4 of Fig. 3, showing the parts separated; and

Fig. 5 is a schematic view showing how the slips may be cut.

It is common at the present time of use circular discs cut from a sheet of grit-coated fabric and having a center opening for mounting them in overhanging relation at the end of a rotary spindle, a portion of the disc at one side of the central spindle being applied to the work. It may be supported on a rubber pad or the like or some other backing element, or sometimes the grit is applied to a relatively stiff backing disc in the first instance. The end of the spindle is usually exposed at the center of the disc and when a flat surface is being worked on the axis of the element is inclined to the surface of the work and the portion of the disc which engages it is bent back while it is in such engagement. Only the radially outward portion of the disc is efiiciently utilized and the central portion of the circle is wasted. The material is expensive. As the outer portion wears the work must be stopped while it is replaced and the life of a single disc is short.

Referring to Figs. 2, 3 and 4, we provide a rotary element for similar mounting in which the grit-coated fabric is used only in the outer annular portion of the circle and is arranged in plurality of plies for longer life as will appear from the following description of the illustrative embodiment shown by way of example in the accompanying drawings.

Referring to Figs. 2, 3 and 4 in the form of the invenand it is preferred to utilize at least three.

tion shown in the drawings the rotary element comprises a backing member or disc 10, Figs. 3 and 4, which may be made from impregnated pressboard of substantial stifiness and which has a central perforation to receive a driving shaft. The outer annular zone of the disc is covered by a'multiplicity of slips 12 of grit-coated sheet material with their grit-coated surface facing away from the disc. One of these slips is shown separate in Fig. 2a and it will be seen that it has generally the form of a truncated sector, being generally trapezoidal in form. The slips, because of their small area, are inherently self-supporting and shape-maintaining, but they are yieldably bendable under imposed forces. They are not flaccid and they do not operate in the manner of loose flaps. These slips are laid in a continuous closed circular series one overlapping the other. Fig. 2a shows one of the slips separate and indicates by contrast with Fig. 2 how much of the gritcoated surface of the slip is covered by overlapping slips. If we are able to pull out radially one of the strips from the assembly of Fig. 2, it would appear as in Fig. 2a. Referring to Fig. 3, we might consider the strips at the right as having been assembled on the backing of the disc in overlapping relation. The series might be continued toward the left in similar manner until the circuit was closed, the final elements being tucked under the first ones to complete the series with all members so overlapping that the exposed portions are the trailing edges when the bufiing element is rotated counterclockwise viewing Figs. 2 and 3. We may compare the overlapping of the slips to that of shingles, although of course in the case of shingles'the shingles in successive courses are staggered. The width of the portion of the slip which isexposed in a sub-multiple of the width of the strip to provide a multi-ply covering. Thus, any line drawn parallel to the axis in the area of the outer annular zone of the element will intersect a plurality of slips. Thus, referring to Fig. 4, the sectioning plane 44 is below, viewing Fig. 3, the edge of the slip 12a immediately above the same in that figure. This slip 12 appears in full in Fig. 4, but four slips 12, as seen in Fig. 4, are cut by this plane. Two plies of strips would illustrate the principle of the invention, but in practice somewhat ineificiently, Four as shown, or five may be used. To revert to the analogy of shingles, the strips as shown in the drawing are laid with one-fourth of their width to the weather.

When the element is rotated clockwise viewing Figs. 2 and 3, the exposed edges trail and contact with the work smooths them down. In Fig. 1, because of the small size of the figure, the slips are exaggerated in thickness. The surface of the element in fact appears substantially flat instead of markedly stepped as might be concluded from Fig. 1.

While the dimensions are not critical, we may state that the drawing represents an actual element 8% inches in diameter with a spindle hole of an inch in diameter. The backing disc was about 5 thick. The slips were of a depth to cover a little more than half the radius of the backing disc and in the completed structure a little less than one-half of the depth Was exposed. The slips were approximately two hundredths of an inch thick.

The slips 12 are disposed entirely at the nearest side of the backing disc 10 and are secured along their radially underlying edges, preferably without folding the edges over, fiatwise against the face of that d.sc along a relatively narrow zone, indicated in Fig. 3 by the stippling at 14 which represents the layer of adhesive. The greater portion of the width of the slips is free toward the trailing edge. The inner ends of the strips are also confined against the backing disc 10 herein by a relatively small disc 16 overlapping the same. In practice a filler 18 As seen from Fig. 5 the slips 12 may be economically cut from a strip S of grit-coated fabric of suitable width by alternating angular cuts 22 and straight cuts 24, producing as seen at the left of the figure, trapezoids one of the non-parallel sides of which is, in the example shown, at right angles to the parallel sides. The shorter parallel sides approximate sufficiently the circular arc of the margin of the filler 18 and may be left. straight when making the disc. straight in Fig. 3.

It has been attempted to show them The longer parallel sides are trimmed after assembly to the desired circular shape of the rotary element producing the truncated sector of Fig. 2a. The amount of the inner ends of the slips which is covered by disc 16 is small as compared with the central portion of a full-sized disc.

When the element is in use, as the grit on the exposed face is used up the fabric supporting it is worn threadbare and disintegrates. Fresh surfaces of grit carried by the underlying slips are exposed. Theoretically a four-ply disc as illustrated is the equivalent of four circular discs superposed. This theoretical life is approached in practice. The section however is different from what would occur if four completely circular discs were on a single spindle because the wasting away of the supporting fabric in the disc first used would not proceed in the same manner.

An important feature of the invention is that, while the slips in general lie flat, after they are bent over by contact with the work they recover the radial position when they pass away from it, one after another, with a relative working between them of slight amplitude. This causes what may be called a breathing action circulating air between the slips. The result is that the element runs cool and lasts longer.

We are aware that the invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and we therefore desire the present embodiment to be considered in all respects as illustrative and not restrictive, as is in fact clear in several matters from the description itself. Reference is to be had to the appended claims to indicate those principles of the invention exemplified by the particular embodiment described and which we desire to secure by Letters Patent.

We claim:

l. A rotary abr-ading element of the type in which the radial face engages and operates on the work comprising a backing disc having a central opening for mounting on a spindle, the radially outward annular portion of the disc being overlaid by a multiplicity of substantially trapezoidal slips of grit-coated sheet material, the slips as such being of such stiffness as to render them inherently self-supporting and shape-maintaining but being yieldably bendable under imposed forces, the slips serially overlapping in a closed circular series, the width of the portions of the slip exposed being a submultiple of the width of the slips to provide a multi-ply covering wherein any axially extending line intersects a plurality of slips, all portions of the slips being exterior to the underlying face of the disc and having areas adjacent the underlying edge secured flatwise to that face, the inner ends of the slips also being confined against the disc.

2. A rotary element as in claim 1 wherein the inner ends of the slips are confined by the overlying margin of a relatively small disc secured to the central portion of the backing disc in the area inward of the circuit of slips.

3. A rotary element as in claim 2 wherein a circular filler is secured to the backing disc with its outer circumference underriding the circuit of slips and the relatively small disc is secured to said filler and thereby to the backing disc.

References Cited in the file of this patent UNITED STATES PATENTS 1,176,001 Stewart Mar. 21, 1916 1,869,564 Johnston Aug. 2, 1932 2,146,548 Mitschang et al. Feb. 7, 1939 2,819,567 Hall Jan. 14, 1958 

